Nano technology is the study and treatment of substance and material in a nano meter range. Nanometer equals to 10−9 meter. The internationally acclaimed range for research and study for the nano technology is between 0.1 nm and 100 nm. The technology has been used in medicine including drug carrier, cell dye, cell separation, clinical diagnosis, and disinfection.
When, compared with conventional metal micro particles, metal nano particles exhibit excellent qualities such as increased surface-to-volume ratio, elevated surface energy, increased ductility after pressure loading, higher hardness, larger specific heat and the like (C. Suryanarayana, P. R. Froes, Metallurgical Transactions A 1992, 23,1071).
Nano particle are extremely important materials with utility in different areas ranging from nanotechnology, non-linear optics, diode lasers smart sensors, markers in drugs, gene sequencing to catalysts. Therefore, the applicability of metal Nano particles receives the extensive interest of the material—directed industry and science. For example, catalytic reaction in which an advantage of high conversion ratio on the catalytic reaction of unsaturated hydrocarbon is noted especially (L. N. lewis, Chern., Rev. 1993, 93, 2693). Metal nano particles have wide applications in different industries like agricultural, poultry and livestocks, textile, polymer, etc.
Metal including silver, copper, mercury, and zinc are known for antibacterial properties. Bacteria treated by these metals do not acquire resistance to the metals. Therefore, the bacterial metals have advantages over the conventional antibiotics which often cause the selection of antibiotic resistant microorganism.
Attempts have been made in the prior art to produce silver-based solution, including colloidal silver, some of which have been more successful than others. Many of the presently available silver-based products, however, are unstable and lose the silver to precipitation. A true colloid operates to maintain the colloidal particles in suspension over a period of several years, and perhaps indefinitely.
Conventionally, silver nano particle have been prepared by various methods such as co-precipitation methods in aqueous solution, electrochemical methods, aerosol, reverse micro emulsion, chemical liquid deposition, photochemical reduction, chemical reduction in solution and UV irradiation. But all of these methods have limitation in controlling the particle size and production of particles on an industrial scale. To overcome these limitations, recently, surfactants, have been used (WO99/43427).
There are also many methods for the preparation of nano-size colloidal metal particles. For example U.S. Pat. No. 6,572,673 disclosed a process for preparing metal nano particles, comprising reacting suitable metal salt and anionic surfactant containing an anionic group of carboxylic group, sulphate group, or sulfonate group as reducing agent in water under reflux at a temperature of 50-140° C.
U.S. Pat. No. 6,979,491 disclosed that nano particles are prepared without the use of ammonia or ammonia water. The antimicrobial yarn is preferably used in making cloth particularly for treatment of patients with burns or wounds.
U.S. Pat. No. 6,660,058 disclosed the preparation of silver alloyed with other elements such as platinum (Pt), palladium (pd), gold (Au) aluminum (AI), cadmium (Cd), and sulfur (S) in surfactant solution. Therefore, it would be advantageous to provide a method for making the colloid nano Silver very simple, fast, and easy to carry over.